1. Field of the Invention
The present invention relates generally to holographic stereograms. More particularly, the present invention relates to reducing ghosting in holographic stereograms.
2. Description of the Related Art
A holographic stereogram is a type of hologram composed or synthesised from a set of two-dimensional views of a subject which are sequentially recorded as holographic elements (hologels) on a holographic recording medium.
FIG. 1 illustrates a process for forming a horizontal-parallax-only stereogram 10. Source data 12, in the form of a plurality of source data frames 14 containing two-dimensional views of an object 15, is input into a processor 16, where each of the source data frames 14 is sectioned. Each section 18 of the source data frames 14 is then distributed using a re-mapping algorithm (e.g. by the methods of Re-Centring, Panning or Rotating, which refer to the way the subject is captured by a video camera) to form a plurality of pre-distort images 20, which is input into a spatial light modulator (SLM) 22 such as a liquid crystal display (LCD). The pre-distort images 20 are subsequently projected through a converging lens 24 (which tends to be a very complicated assembly of lenses) onto a holographic recording medium 26 such as photopolymer.
The converging lens 24 compresses the pre-distort images 20 into a plurality of holographic elements 28, each of which is sequentially recorded onto the holographic recording medium 26 to form the holographic stereogram 10.
FIG. 2 illustrates a set of source data 12 and a corresponding set of images 30 reproduced from the holographic stereogram 10 generated by the method illustrated in FIG. 1. This is a rough depiction of what the viewer sees in real life. Brightness, contrast, etc. could differ. Ideally, the holographic stereogram 10 provides an accurate reproduction of the source data 12. Often, however, shadows appear in the images 30 reproduced from the holographic stereogram 10 as illustrated in FIG. 2. The presence of “shadows” in the images 30 reproduced from the holographic stereogram 10 is known as ghosting. The ghosting phenomenon reproduces the images 30 inaccurately on the holographic stereogram.
In view of the foregoing, it is desirable to provide a method for forming a holographic stereogram wherein ghosting in images reproduced from the holographic stereogram is reduced or eliminated, in order that the final stereogram images resembles the original images 30 as accurately as possible.